christoph/lecture-compilers
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fix bug where rotations were missing

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ChUrl
2020-12-12 17:34:30 +01:00
parent 16315e288a
commit 9d998d625d
1 changed files with 30 additions and 18 deletions
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48
src/main/java/parser/ast/ExpressionBalancer.java
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@ -1,11 +1,25 @@
package parser.ast; package parser.ast;
import java.util.Collections;
import static util.Logger.log;
public final class ExpressionBalancer { public final class ExpressionBalancer {
private ExpressionBalancer() {} private ExpressionBalancer() {}
// Spiegelt den Baum, da meine Müll-Grammatik die EXPRs rückwärts parst public static void balance(AST tree) {
flip(tree);
leftPrecedence(tree);
operatorPrecedence(tree);
log(tree.toString());
log("-".repeat(100));
}
// Baum spiegeln, damit höhere Ebenen links sind und EXPR vorwärts laufen
public static void flip(AST tree) { public static void flip(AST tree) {
log("Flipping expressions");
flip(tree.getRoot()); flip(tree.getRoot());
} }
@ -14,25 +28,18 @@ public final class ExpressionBalancer {
flip(child); flip(child);
} }
if (root.getChildren().size() == 2) { Collections.reverse(root.getChildren());
Node left = root.getChildren().get(0);
Node right = root.getChildren().get(1);
root.setChildren(right, left);
}
} }
// Führt Linksrotationen durch // Führt Linksrotationen durch
// Es werden EXPR-Nodes (2 Childs, 1 davon EXPR, Kein Wert) solange wie möglich linksrotiert // Es werden EXPR-Nodes (2 Childs, 1 davon EXPR, Kein Wert) solange wie möglich linksrotiert
public static void leftPrecedence(AST tree) { public static void leftPrecedence(AST tree) {
boolean change; log("Rotating expressions for left-precedence");
leftPrecedence(tree.getRoot());
do {
change = leftPrecedence(tree.getRoot());
} while (change);
} }
private static boolean leftPrecedence(Node root) { // Es wird solange rotiert bis die letzte "Rotation" durchgeführt wurde
private static void leftPrecedence(Node root) {
for (Node child : root.getChildren()) { for (Node child : root.getChildren()) {
leftPrecedence(child); leftPrecedence(child);
} }
@ -40,15 +47,18 @@ public final class ExpressionBalancer {
Node expr = getExpr(root); Node expr = getExpr(root);
if (expr == null || root.getChildren().size() != 2 || !root.getValue().isEmpty()) { if (expr == null || root.getChildren().size() != 2 || !root.getValue().isEmpty()) {
return false; return;
} }
leftRotate(root); boolean change;
return true; do {
change = leftRotate(root);
} while (change);
} }
private static void leftRotate(Node root) { // Die Letzte Rotation ist keine richtige Rotation, dort wird false zurückgegeben
private static boolean leftRotate(Node root) {
Node left = root.getChildren().get(0); Node left = root.getChildren().get(0);
Node right = root.getChildren().get(1); Node right = root.getChildren().get(1);
@ -57,7 +67,7 @@ public final class ExpressionBalancer {
root.setName(right.getName()); root.setName(right.getName());
root.setValue(right.getValue()); root.setValue(right.getValue());
root.setChildren(left, right.getChildren().get(0)); root.setChildren(left, right.getChildren().get(0));
return; return false;
} }
Node insertLeft = new Node(root.getName()); Node insertLeft = new Node(root.getName());
@ -66,6 +76,8 @@ public final class ExpressionBalancer {
root.setName(right.getName()); root.setName(right.getName());
root.setChildren(insertLeft, right.getChildren().get(1)); root.setChildren(insertLeft, right.getChildren().get(1));
return true;
} }
private static Node getExpr(Node root) { private static Node getExpr(Node root) {